Cd(II) removal from phenols-bearing wastewater using magnetic carbon nanotubes

Abstract

This project studied Cd(II) uptake from phenols-bearing wastewater using magnetic carbon nanotubes (MCNT) as adsorbent. Initially, Cd(II) complexation with various phenols was confirmed by FT-IR spectroscopy. Factors affecting Cd removal are: solution pH; type of phenol [phenol (Ph), 2-chlorophenol (2-CP), 2-nitrophenol (2-NP), and 2,4-dinitrophenol (2,4-DNP)]; Mag:CNT mass ratio; Cd:phenolic compound molar ratio; and the effect of order of adding adsorption components (MCNT, Cd(II), phenolic compound) to the extraction medium. It was found that the presence of phenols in the extraction medium caused a 10–50% decrease in Cd(II) uptake. This was probably due to a competition between phenols/surface functional groups towards Cd(II); or phenols/Cd(II) to occupy the surface functional groups. 2,4-DNP was selected as a model phenolic compound. The optimum adsorption conditions [1:1 M ratio of (Cd(II):2,4-DNP) at pH 6 using MCNT(1:1) adsorbent] resulted in adsorption capacity of 17.9 mg Cd g−1. The best order of adding reagents was (Cd(II) + MCNT(1:1)) and then 2,4-DNP. The regeneration of the adsorbent was possible by using 0.5 M HNO3 where 90% of adsorption efficiency was reserved after three times of successive use. Upon presence of co-existing ions, 75% of the adsorption efficiency was maintained. The applicability of the proposed adsorption method on real water samples was evaluated.